• 8.0 baseline — 0.6 × season 8.2 (19 gm) + 0.4 × last 10 7.7
• +0.2 opponent leak — they concede 219.2/game vs a 213.6 league average
• +1.5 at this ground — averages 9.5 there (86 gm)
• vs them: averages 9.6 over 13 games — evidence, never summed

Derived, not measured — plain arithmetic over his real games, shown in full. Adjustments can overlap (a game at this ground can also be a wet one); they add simply, and this note is the admission. Round 20: 15 — far outside his usual range; kept in the average, not smoothed away.